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Zak, Physiology > Skeletal Muscle Contraction > Flashcards

Skeletal Muscle Contraction Flashcards

0
Q

Epimysium

A

Connective tissue surrounding the entire muscle

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1
Q

What is the hierarchical organization of skeletal muscle

A

Epimysium->Muscle->Perimysium->Fascicle->Endomysium->Sarcolemma->Myofiber->Myofibril->Myofilament (sarcomere)

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2
Q

Muscle components

A

Made of multiple fascicles

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3
Q

Perimysium

A

Connective tissue covering individual fascicles

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4
Q

Fascicle

A

A bundle of myofibers

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5
Q

Endomysium

A

Connective tissue lining each myofiber

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6
Q

Sarcolemma

A

Cell membrane of muscle fiber (aka, plasmalemma)

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7
Q

Myofiber

A

Individual, multinucleated muscle cell (aka, muscle cell)

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8
Q

Myofibril

A

A chain of sarcomeres within a muscle fiber/muscle cell

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9
Q

Myofilament

A

Actin and myosin filaments that make up a sarcomere

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10
Q

What do T-tubules do and where are they found?

A

Found in the sarcolemma, close to the cisternae of the SR… They transport the action potential through the muscle cell

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11
Q

What are the bands of a sarcomere and what do they contain

A

Z-disc: at ends of sarcomere, anchors actin filaments I-band: composed of only actin, width changes H-band: composed of only myosin, width changes A-band: composed of entire myosin filament and a portion of actin filament, width does not change M-line: formed when H-band brings together actin filaments forming the M-line

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12
Q

Explain the process of muscle contraction

A

1)Action potential reaches end of axon opening voltage-gated channels releasing ach into synaptic cleft, which open ligand-gated Na+ channels sarcolemma, generating action potential in sarcolemma 2)Action potential in sarcolemma travels down T-tubules to the DHP which interacts with ryanodine-receptors to release Ca++ from SR into cytosol 3)Ca++ binds to troponin which moves tropomyosin off of myosin binding sites on actin and myosin filaments walk down actin filaments 4)Ca++ is pumped back into SR by active transport and also sequestered by calsequestrin

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13
Q

What are DHP receptors

A

Voltage-gated channels on T-tubules of sarcolemma that cause a change in ryanodine receptors allowing Ca++ to leave SR and enter cytoplasm

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14
Q

What are Ryanodine receptors and SERCA

A

Ryanodine receptors (RyRs) are on the cisternae of the SR and respond to a conformational change in the DHP receptors allowing Ca++ to flow into the cytoplasm… SERCA= ATPase pump that pumps Ca++ back into the SR

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15
Q

Calsequestrin

A

Helps maintain the proper Ca++ concentration in the SR and cytoplasm by binding to Ca++ and bringing it back in the SR after contraction

16
Q

When is there no tension on the muscle

A

When the sarcomere is fully relaxed and there is no interaction b/w myosin and actin

17
Q

When does tension on the muscle begin and reach its max

A

When the actin and myosin begin interacting, tension begins…tension reaches its max when the actin filaments come together and the M-line is formed…after that, tension begins to decrease again

18
Q

Where is ATP used during muscle contraction

A

Mainly during sliding filament mechanism…pumping Ca++ back into the SR and Na+ and K+ ions out and into the cell to repolarize the cell

19
Q

How much ATP is available for contraction…

A

1-2 seconds worth

20
Q

How does the phosphocreatine energy system work

A

It reconstitutes the ATP and provides enough energy for 5-8 seconds of contraction

21
Q

How does glycolysis contribute to muscle contraction

A

Allows for ~1 minute of contraction, but causes build up of lactic acid

22
Q

What is the main energy source for longterm muscle contraction

A

Oxidative Phosphorylation…accounts for ~95%

23
Q

Isometric Contraction

A

Causes increase in tension, but not muscle length

24
Q

Isotonic Contraction

A

Causes increase in tension and change in length… 2 types: Concentric & Eccentric

25
Q

Concentric Muscle Contraction

A

Occurs when the muscle shortens

26
Q

Eccentric Muscle Contraction

A

Occurs when the muscle lengthens

27
Q

Fast Twitch Fibers

A

Contract rapidly but have low endurance… Few mitochondria & myoglobin, larger amount of ATPase… Primarily uses anaerobic respiration… White in color

28
Q

Slow Twitch Fibers

A

Contract slower but have high endurance… More mitochondria & myoglobin, less ATPase… Primarily uses aerobic respiration… Reddish in color

29
Q
A

A) DHP

B) Ca++

C) Terminal Cisternae

D) SR

E) Ca++ Release Channel (RyRs)

F) Ca++

G) RyRs

H) Calsequestrin

I) Ca++

30
Q
A

1) Myofibrils
2) Z line
3) Triad of the reticulum
4) A band
5) I band
6) T-tubule
7) SR
8) T-tubule
9) Terminal Cisternae
10) Sarcolemma

Zak, Physiology (20 decks)

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